United will be operating the Dreamliner on new and existing routes, and while we don't know exactly where the 787 will fly first, service is slated begin later this year. The first confirmed route will launch on March 31st between Denver and Tokyo, growing direct service between the Japanese hub and the U.S. to 10 cities (including Honolulu and Guam). Passengers on board those flights will certainly appreciate the oversized dimmable windows and giant overhead bins, along with all-LED lighting, which sadly are limited to basic color configurations, rather than the ANA we've seen during boarding on ANA.

The 787 is more than a foot narrower than the 777, but United maintained the same seating configuration as its Continental acquisitions, which you might assume makes the aircraft seem a bit cramped. The higher ceilings and open feel made the difference almost unnoticeable, however, and the Continental-era BusinessFirst seats on board are still far superior to United's own triple-7 layout, where four center seats mean you could end up paying for a bed yet still have a middle seat. Here, just like on those select triple-7s (mostly used on flights beginning in Houston or Newark), biz seats offer much more privacy, with more personal space and substantial dividers.

Gallery: United Dreamliner Interior

In the Y-cabin, seats seemed cushier than what we've used on United's existing fleet, and feature the same in-flight entertainment system installed on some of the carrier's current aircraft. Like BusinessFirst, these seats also feature larger dimmable windows and overhead bins which reportedly offer 30 percent more capacity than those on United's 777. Rows 16 and 27 have substantially more legroom than other Economy Plus seats. In fact, there's so much space between the window-side seats in row 27 that you could plop down a sleeping bag and camp out on the floor if the FAA permitted it.

Surprisingly, the most spacious seats on the plane aren't in this row or even in the business cabin, but instead are located up a flight of stairs in a hidden second level. Two sets of crew quarters are located at the far forward and far aft positions, behind doors marked "Crew Only." Through those doors and up a small flight of stairs you'll find two full-size beds in the front of the Dreamliner and six in the rear. There's not much room to do much other than sleep, but thick, full-length mattresses will surely enable pilots and flight attendants to make good use of scheduled rest periods.

We felt quite comfy during our visit to United's 787, even on the main level, and while we couldn't experience the boosted humidity, increased cabin pressure, noise suppression and computer-assisted smooth performance, it's clear that the Dreamliner will be very popular among United passengers. There's a few months to go until you can take a flight of your own, but we have plenty of photos to tide you over for now. Thumb through the galleries for a closer look, then scroll down below for a hands-on video from Engadget.